Nanodiamonds are metastable allotropes of carbon. Based on their high hardness, chemical inertness, high thermal conductivity, and wide bandgap, nanodiamonds are widely used in energy and engineering applications in the form of coatings, such as mechanical processing, nuclear engineering, semiconductors, etc., particularly focusing on the reinforcement in mechanical performance, corrosion resistance, heat transfer, and electrical behavior. In mechanical performance, nanodiamond coatings can elevate hardness and wear resistance, improve the efficiency of mechanical components, and concomitantly reduce friction, diminish maintenance costs, particularly under high‐load conditions. Concerning chemical inertness and corrosion resistance, nanodiamond coatings are gradually becoming the preferred manufacturing material or surface modification material for equipment in harsh environments. As for heat transfer, the extremely high coefficient of thermal conductivity of nanodiamond coatings makes them one of the main surface modification materials for heat exchange equipment. The increase of nucleation sites results in excellent performance of nanodiamond coatings during the boiling heat transfer stage. Additionally, concerning electrical properties, nanodiamond coatings elevate the efficiency of solar cells and fuel cells, and great performance in electrochemical and electrocatalytic is found. This article will briefly describe the application and mechanism analysis of nanodiamonds in the above‐mentioned fields.